/**
 * @file methods/ann/layer/add_merge_impl.hpp
 * @author Marcus Edel
 *
 * Definition of the AddMerge module which accumulates the output of the given
 * modules.
 *
 * mlpack is free software; you may redistribute it and/or modify it under the
 * terms of the 3-clause BSD license.  You should have received a copy of the
 * 3-clause BSD license along with mlpack.  If not, see
 * http://www.opensource.org/licenses/BSD-3-Clause for more information.
 */
#ifndef MLPACK_METHODS_ANN_LAYER_ADD_MERGE_IMPL_HPP
#define MLPACK_METHODS_ANN_LAYER_ADD_MERGE_IMPL_HPP

// In case it hasn't yet been included.
#include "add_merge.hpp"

#include "../visitor/forward_visitor.hpp"
#include "../visitor/backward_visitor.hpp"
#include "../visitor/gradient_visitor.hpp"

namespace mlpack {
namespace ann /** Artificial Neural Network. */ {

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
AddMerge<InputDataType, OutputDataType, CustomLayers...>::AddMerge(
    const bool model, const bool run) :
    model(model), run(run), ownsLayers(!model)
{
  // Nothing to do here.
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
AddMerge<InputDataType, OutputDataType, CustomLayers...>::AddMerge(
    const bool model, const bool run, const bool ownsLayers) :
    model(model), run(run), ownsLayers(ownsLayers)
{
  // Nothing to do here.
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
AddMerge<InputDataType, OutputDataType, CustomLayers...>::~AddMerge()
{
  if (!model && ownsLayers)
  {
    std::for_each(network.begin(), network.end(),
        boost::apply_visitor(deleteVisitor));
  }
}

template <typename InputDataType, typename OutputDataType,
          typename... CustomLayers>
template<typename InputType, typename OutputType>
void AddMerge<InputDataType, OutputDataType, CustomLayers...>::Forward(
    const InputType& input, OutputType& output)
{
  if (run)
  {
    for (size_t i = 0; i < network.size(); ++i)
    {
      boost::apply_visitor(ForwardVisitor(input,
          boost::apply_visitor(outputParameterVisitor, network[i])),
          network[i]);
    }
  }

  output = boost::apply_visitor(outputParameterVisitor, network.front());
  for (size_t i = 1; i < network.size(); ++i)
  {
    output += boost::apply_visitor(outputParameterVisitor, network[i]);
  }
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
template<typename eT>
void AddMerge<InputDataType, OutputDataType, CustomLayers...>::Backward(
    const arma::Mat<eT>& /* input */,
    const arma::Mat<eT>& gy,
    arma::Mat<eT>& g)
{
  if (run)
  {
    for (size_t i = 0; i < network.size(); ++i)
    {
      boost::apply_visitor(BackwardVisitor(boost::apply_visitor(
          outputParameterVisitor, network[i]), gy,
          boost::apply_visitor(deltaVisitor, network[i])), network[i]);
    }

    g = boost::apply_visitor(deltaVisitor, network[0]);
    for (size_t i = 1; i < network.size(); ++i)
    {
      g += boost::apply_visitor(deltaVisitor, network[i]);
    }
  }
  else
    g = gy;
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
template<typename eT>
void AddMerge<InputDataType, OutputDataType, CustomLayers...>::Backward(
    const arma::Mat<eT>& /* input */,
    const arma::Mat<eT>& gy,
    arma::Mat<eT>& g,
    const size_t index)
{
  boost::apply_visitor(BackwardVisitor(boost::apply_visitor(
      outputParameterVisitor, network[index]), gy,
      boost::apply_visitor(deltaVisitor, network[index])), network[index]);
  g = boost::apply_visitor(deltaVisitor, network[index]);
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
template<typename eT>
void AddMerge<InputDataType, OutputDataType, CustomLayers...>::Gradient(
    const arma::Mat<eT>& input,
    const arma::Mat<eT>& error,
    arma::Mat<eT>& /* gradient */ )
{
  if (run)
  {
    for (size_t i = 0; i < network.size(); ++i)
    {
      boost::apply_visitor(GradientVisitor(input, error), network[i]);
    }
  }
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
template<typename eT>
void AddMerge<InputDataType, OutputDataType, CustomLayers...>::Gradient(
    const arma::Mat<eT>& input,
    const arma::Mat<eT>& error,
    arma::Mat<eT>& /* gradient */,
    const size_t index)
{
  boost::apply_visitor(GradientVisitor(input, error), network[index]);
}

template<typename InputDataType, typename OutputDataType,
         typename... CustomLayers>
template<typename Archive>
void AddMerge<InputDataType, OutputDataType, CustomLayers...>::serialize(
    Archive& ar, const uint32_t /* version */)
{
  // Be sure to clear other layers before loading.
  if (cereal::is_loading<Archive>())
    network.clear();

  ar(CEREAL_VECTOR_VARIANT_POINTER(network));
  ar(CEREAL_NVP(model));
  ar(CEREAL_NVP(run));
  ar(CEREAL_NVP(ownsLayers));
}

} // namespace ann
} // namespace mlpack

#endif
